Bird flu wiped out poultry, and now the screwworm is coming for beef

Straits Times

30-07-2025

AUSTIN, Texas – First came bird flu, which led to the culling of large swaths of the nation's poultry flocks and the soaring egg prices that helped undermine President Joe Biden's reelection. Now, ranchers in Texas and officials at the Agriculture Department are raising the next alarm: the New World screwworm.
Texas livestock producers and ranchers fear that the United States is ill-equipped to handle a potential outbreak of screwworm, whose incursion into the country appears increasingly likely. With beef prices already soaring, the screwworm, whose Latin name roughly translates to 'man-eater,' is a real threat, to both cows and the cost of living for America's meat lovers.
'If we wait, we lose,' Mr Stephen Diebel, vice-president of the Texas and Southwestern Cattle Raisers Association, told state lawmakers during a hearing in Austin this month as he pleaded for intervention.
The screwworm, like the measles, may have been forgotten by many, but it's not new. And like the measles, which has cropped up in Texas recently, screwworm was once all but eradicated from the United States.
Infestations occur when a female fly lays eggs, between 10 and 400 at a time, on a fresh animal wound. Within a few hours, the eggs hatch into larvae that burrow and feed on the flesh. As the wound worsens, it attracts more flies, which lay more eggs. After about a week, adult screwworm flies can reproduce and begin the cycle all over again. The parasitic infection can kill a cow within two weeks if left untreated. There is currently no approved treatment.
'It's like something out of a horror movie,' the Texas agriculture commissioner, Mr Sid Miller, said in an interview. He saw distressed cattle infested with screwworm when he was a child in the early 1960s before it was nearly eradicated. 'It's quite a putrid sight,' he said.
Livestock, wildlife, pets and, in rare cases, humans can be affected.
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In the 1950s, scientists discovered that radiation effectively sterilises screwworm flies, and the federal government began an eradication program. A small outbreak in a deer population in the Florida Keys was snuffed out in 2017.
Now, a potentially bigger threat is approaching, migrating north from South America, where screwworm is endemic. It has been detected as close as 370 miles (595km) from Texas' border, carried by the surge of animals coming through the Darien Gap, a once largely impenetrable jungle area that separates South America and Central America.
A joint eradication effort between the United States and Panama has largely kept screwworm south of Central America for decades. Illegal livestock transport and warm weather patterns have also contributed to the worm's climb north, a spokesperson for the Agriculture Department said.
'For small herds, it could wipe us out,' said Ms Shelbie Pippenger, who, with her husband, has a small herd in Texas and helps manage other ranches. 'Once something starts, it's difficult to stop it.'
Agriculture Secretary Brooke Rollins announced in June an US$8.5 million (S$10.95 million) initiative based in Texas that will produce sterile male screwworm flies and then drop them into affected areas. Female flies mate only once in their lifetime, so the sterile flies eventually overwhelm and eradicate the pest.
Ms Rollins also committed US$21 million to renovate a fly production facility in Mexico, where 60 million to 100 million sterile male flies would be produced each week for use in Mexico or Texas by the end of the year.
But that effort would yield only about 20 per cent of the sterile flies the United States would need to manage an outbreak, experts said. Around 600 million flies were released each week to eradicate screwworm decades ago. Senator John Cornyn introduced legislation that would provide US$300 million to construct a facility to breed and sterilise flies, but the House has left Washington for the summer.
'We are desperately short on sterile fly production,' Mr Diebel said.
Even before the fear of pestilence, the industry was facing challenges. Drought and high feed prices have pushed the American cattle inventory to the lowest it has been since 1952, according to the Agriculture Department.
Domestic beef prices hit record highs in May, at an average of US$5.98 per pound for ground beef, according to the Bureau of Labor Statistics. Beef from Brazil, the world's largest beef exporter, could bring some price relief, although President Donald Trump has promised to impose a 50 per cent tariff on Brazilian imports, beginning in August.
And now, the screwworm is threatening to wipe out whole cattle herds in the United States.
The tusklike mandibles protruding from the screwworm larva's mouth. The larva, left by a parasitic fly on a fresh animal wound, attracts more flies eventually killing a cow within two weeks.
PHOTO: JOHN KUCHARSKI/U.S. DEPARTMENT OF AGRICULTURE/NYTIMES
Before the screwworm was eradicated, US beef producers experienced as much as US$20 million of economic loss each year from animal deaths, decreased livestock production, increased veterinary costs and other expenses, according to the Agriculture Department.
Texas Governor Greg Abbott did not respond to questions about whether he would approve state funding for a fly factory. Mr Abbott has directed the Texas Parks and Wildlife Department and the Texas Animal Health Commission to create a response team to lead the state's screwworm preparations.
Meanwhile, based on how fast the screwworm is traveling, Mr Miller said it could reach Texas within four months.
In economic terms, the screwworm is already here, modestly at least. About 3 per cent of US cattle come from Mexico, but citing inadequate surveillance of screwworm, the Agriculture Department cut off imports of Mexican cattle in November 2024. Federal officials resumed the trade in February after Mexico put in place more rigorous inspection protocols. But imports were shut off again in May after the pest was detected in Veracruz and Oaxaca. NYTIMES